With the completion of the human genome project, attention is shifting towards individual genetic variation. Such variation, most of which consists of single nucleotide polymorphisms (SNPs), may account for a substantial portion of human individual phenotypic variation, including differences in aging-related characteristics. Especially important are SNPs that affect the function of genes in candidate longevity assurance pathways, since they could provide novel targets for the early detection and possible prevention of aging-related functional decline. Optimal study populations in this respect are those in which aging related phenotypes can be defined in terms of their progression from middle age onwards, rather than as snapshots in time. We hypothesize that genetic variation at loci involved in genome maintenance can be related to individual differences in the rate and severity of aging. To address this hypothesis, a systematic multidisciplinary study is proposed in which SNP haplotypes of about 100 genes in 5 genome maintenance pathways will be determined in individuals of an ongoing longitudinal study of 586 Mexican American (MA) and 428 European American (EA) (SALSA; San Antonio Longitudinal Study of Aging). Subsequent association analysis in conjunction with functional assays of allelic gene variants will provide insight into their biological significance. The results should lead to increased understanding of the role of genome maintenance in healthy aging and provide genetic markers to identify individuals at risk for specific aging related phenotypes. This will open up the possibility of targeted and personalized intervention strategies, ultimately leading to improved quality of life of the elderly population.